1. Field of the Invention
The present invention relates to an imaging apparatus that exchanges information with an interchangeable lens by communication, and an interchangeable lens that can be mounted on the imaging apparatus.
2. Description of the Related Art
Conventionally, synchronous serial communication that uses a clock signal has been employed as a communication method between a camera, which serves as an imaging apparatus, and an interchangeable lens that can be mounted on the camera. Japanese Patent No. 3658084 discusses the following technical subject matter. First, synchronous serial communication is performed with an interchangeable lens at a first communication speed at which communication is possible even for an old type of interchangeable lens. Based on the communication contents, if a camera microcomputer determines that the mounted interchangeable lens is a new type of lens, the camera microcomputer switches to synchronous serial communication capable of communication at a faster second communication speed. Further, Japanese Patent No. 3658084 also discusses that, during this communication speed switch, the camera microcomputer switches the communication terminal circuits from an open drain type to a complementary metal-oxide-semiconductor (CMOS) type that is suited to high-speed communication. According to this technology, a system is realized in which, when an old type of interchangeable lens is used, operation is possible even though the speed is slow, while when a new type of interchangeable lens is used, the communication speed is improved to a constant high level.
However, for conventional synchronous serial communication, no matter how much the clock speed is increased, there is a wait between communications. Consequently, there is a limit to how much the operation performance, which includes communication between the camera and the interchangeable lens, can be improved.